In the conventional perpetual calendars, one can manually change date, week-day, and month by replacing a group of pages everday. In case of loss of the date and week-day, or when a long period of time has lapsed, the calendar may become useless or very difficult to reset, and therefore it is deemed not an ideal perpetual calendar. Another kind of perpetual calendar can have its date, week-day, and month changed by a rotating means operated manually every day; it is considered also as being not a practical perpetual calendar because one can easily forget to make a proper change of dates.